A standard reproducible method for determining the potency of inactivated poliovirus vaccines (IPV) in vitro would be an important advance toward the eradication of polio. Protection against polio is provided by neutralizing antibodies with "D" antigen specificity. We have developed an ELISA test in which monoclonal antibody (which is "D" specific) is used for detection. Using our reagents as the standard we examined sera from other collaborating laboratories for the ability to measure the potency of IPV. We were able to examine polyclonal capture or detection sera prepared in four different species including: rabbits, cows, horses and goats. We were also able to compare two different vaccine preparations of IPV, one made from wild poliovirus and the other from Sabin strains. Furthermore, we were able to examine polyclonal sera prepared with either the wildtype or Sabin strains of poliovirus. We have found that reagents prepared against wildtype poliovirus strains react well in the ELISA with Sabin derived IPV and vice versa. The majority of monoclonal antibodies react well with wild or Sabin derived vaccines irrespective of the strain used in their preparation. These findings suggest that the attenuated strains (Sabin) when prepared as an inactivated vaccine retain antigens in common with the inactivated wildtype strains. Several monoclonal antibodies were found to be strain specific and a few non-reactive with either strain of poliovirus in the ELISA. Whether equivalent D Ag units in Sabin strain and wild type IPV will provide the same in vivo immunogenicity is not yet known. An ELISA test which incorporates cross-reactive as well as strain specific monoclonal antibodies will be a useful tool for comparing the potency of wild-type and Sabin derived vaccines in vitro.